Plants are a primary source of human and/or animal food, excellent feedstock for fuels, and useful for production of desirable chemicals. Plants synthesize and store lipids, primarily, in cytosolic lipid droplets. In plants, seeds are the primary site of oil synthesis and storage; vegetable oils (such as triacylglycerol) are used as a form of energy during seed germination. Vegetable oils can be synthesized in non-seed (such as leaf) tissues; however, their abundance is low and the stored lipids are presumed to be metabolized rapidly, perhaps for the recycling of fatty acids for energy or the synthesis of membrane lipids.
Plants that can accumulate oils in non-seed tissues are commercially attractive. The biomass of non-seed parts (such as leaves, stems) of plants is generally far greater than the amount accounted for by seeds. Thus, the transformation of non-seed tissues into oil-producing machinery can significantly increase the energy-production capacity. Currently, the regulation and transient accumulation of stored oils in non-seed tissues are not well understood, and the production of oils in non-seed plant tissues for industrial applications remains challenging. Cellular lipid droplets are dynamic organelles that regulate triglyceride storage in mammalian cells. Lipid droplets are composed of a core of neutral lipids surrounded by a phospholipid monolayer and associated proteins. Various lipid droplet-associated proteins, including fat specific protein 27 (FSP27), perilipins, seipin (Bernardinelli-Seip congenital lipodystrophy type 2 protein), FIT1 (fat storage-inducing transmembrane protein 1), and FIT2 (fat storage-inducing transmembrane protein 2) have been well characterized for their ability to regulate fat metabolism in mammalian species.